1. Field of the Invention
The present invention relates to non-animal polymer compositions suitable for film forming, particularly hard and soft capsules, comprising water soluble cellulose ethers, hydrocolloids and sequestering agents.
2. Description of Related Art
Capsules are widely used in the pharmaceutical industry as well as in the health food supplement market. The main usage thereof is as dosage form for solid, semi-solid, liquid, pellet or herbal preparations. A primary objection of these dosage forms is to have a good disintegration after being administered in order to enable an effective dissolution of the active substances in the appropriate digestive organ. Consequently, this disintegration characteristic has to remain stable over time when finished products are stored prior to use.
The traditional material for forming the capsule shell is gelatin, because it has the correct and quite ideal properties. Nevertheless, gelatin has some disadvantages which make it necessary to have other capsule shell materials available. A major unfavorable aspect is the animal origin of gelatin. Other disadvantages are the inconveniences of relatively high water content (10-17%) and the loss of elasticity with decreasing water content. Furthermore gelatin capsules are sensitive to heat and humidity which affects the usability of the product. In particular, soft gelatin capsules are known to aggregate under hot and humid conditions. Under dry conditions gelatin films may induce static charge build up affecting later processing.
As a gelatin substitute the use of water soluble film forming cellulose derivatives is widely described in the literature. Reports of capsules made from cellulose derivatives refer to poor disintegration in vivo especially when compared with gelatin. To overcome this drawback in EP0714656 it is suggested to use hydroxypropylmethylcellulose (HPMC) with a viscosity of 2.4 to 5.4 centistokes in 2% aqueous solution at 20xc2x0 C. with carrageenan as gelling agent and calcium or potassium ions as co-gelling agent. However the very low viscosity of HPMC resulting from lower molecular weight chains induces higher film brittleness. Furthermore, the use of this composition results in an undesirable loss of transparency of the film. Attempts to improve transparency are disclosed in EP0592130 by exposing BPMC to UV radiation prior to capsule processing.
It has been found that a polymer film composition for capsules wherein the ratios of cellulose ethers, hydrocofloids and sequestering agents are 90 to 99.98% by weight of a cellulose ether or mixture of cellulose ethers with a water content of 2 to 10%, 0.01 to 5% by weight of a hydrocolloid or mixtures of hydrocofloids, and 0.01 to 5% by weight of a sequestering agent or agents do not have the mentioned disadvantages.